Speech and music rely on complex patterns of timing, or rhythms, as a vital part of their poser to communicate. Currently, a body of data exists regarding the neuroanatomical localization of other processes involved in the perception of speech and music, but little is known about cortical areas involved in the perception of auditory rhythm. Previous studies have linked this function to the auditory cortices of the temporal lobe, but have not demonstrated more specific contributions of different auditory areas. In particular, the role of primary auditory cortex in perception of rhythm has not been explored. The goal of the research described in this proposal is to investigate the neuroanatomical substrate of rhythm perception through studies of patients with focal lesions, and through neuro-imaging techniques in normal subjects. The three experiments which will form the basis of my doctoral dissertation are: Experiment I. Examination of rhythm perception in patients with right or left anterior temporal-lobectomies including auditory cortex. Experiment II. Magnetic Resonance Imaging (MRI) quantification of surgical removals in auditory cortex. Experiment III. Positron Emission Tomography (PET) study of rhythm perception in normal subjects. Taken together, these studies will generate new information about the neural structures involved in auditory rhythm perception. These data will be of significance for our understanding of the timing mechanisms underlying perception of music and speech. In addition, because the temporal lobe is the most common site of excision for intractable epilepsy, greater understanding of the functions of this area may be useful in the evaluation of surgical candidates and the planning of surgical removals.